Indoor Air

The airflow movement inside a multizone building has a significant impact on pollutant transfer, thermal comfort, and indoor air quality. However, there are difficulties in visualizing the airflow movement with existing methods. This study proposes a visualization method for evaluating airflows between adjacent internal zones inside a multizone building based on the analysis of pressure difference frequency. After the distribution of absolute pressure is measured and the wind pressures on the surfaces of the building are calculated, the variation of pressure differences between each couple of adjacent zones is analyzed for three levels: greater than 0 Pa, equal to 0 Pa, and less than 0 Pa (for any given zones selected as target zones). Finally, an airflow mapping is created for each floor using the visNetwork tool based on the R language. A target building was selected for applying the proposed method. The airflow mappings were derived from a detailed analysis of the pressure difference frequency between each couple of adjacent zones, presenting the variations of airflow direction and the dominant airflow during the measurement period in a visualized form. For example, the airflow direction from 1F_Z2 to 1F_Z3 is 92.0%. The spatial similarity in the variations of the airflow directions can also be observed on certain floors. The results of this experimental study show that the airflows between multiple zones can be easily identified without a complex building zone analysis. The variation in internal airflow direction between adjacent zones can be intuitively visualized, providing insight to the airtightness levels of building components. It is also observed that the airflow rates computed based on the airflow mappings can provide more guidance for the control of HVAC systems.

Indoor air quality can be influenced by various indoor activities. The indoor air pollutants generated by cooking activities can cause severe risks to occupants’ health in residential buildings. The present study conducted field experiments to measure indoor pollutants associated with cooking in 29 residential buildings. Due to an open plan in Korean residential buildings, the emission of indoor pollutants was measured in the kitchen and living room. Focusing on aldehydes, the indoor emission levels for various cooking methods such as grilling, frying, and boiling were analyzed. As a result, the emission of formaldehyde, acetaldehyde, and propionaldehyde was highly increased for all cooking methods. The increase rate of the emission was higher in the kitchen than that in the living room for grilling and frying. In the case of boiling, the highest concentration of aldehydes was observed. Moreover, the indoor level of aldehydes was higher in the living room than that in the kitchen. Moreover, the health risk such as cancer for occupants was assessed based on the measured data for different cooking methods. The assessment results showed that all the emissions of aldehydes for different cooking methods required instant actions to avoid cancer risk for occupants.

Clothing can absorb fine particulate pollutants from the atmosphere outdoors and then release them after entering the room in a form similar to three-handed smoke. In this study, the experimental site in Zhengzhou, a typical city with heavy pollution in central China, was used to investigate the adsorption and diffusion patterns of three different fabrics of polyester, polyester-cotton, and cotton clothing for fine particle pollutants, to guide people’s behavior patterns and indoor air distribution, and to reduce indoor pollution exposure. The results showed that when garments of three different fabrics were exposed to moderate and heavy PM_2.5 pollution for 1 h, 2 h, and 3 h, respectively, and then transferred to the diffusion chamber, polyester always released the highest PM_2.5 concentration to indoor air during the same release cycle, followed by cotton and polyester-cotton. In addition, the concentration of indoor air pollutants will be periodically affected by the diffusion of fine particulate adsorbed by clothing fabrics. With the increase in outdoor pollution and exposure duration, the indoor PM_2.5 concentration takes longer to stabilize at certain levels after the clothing is transferred to the indoor side. Finally, the comparison of natural ventilation experiments proved that it is not feasible to rely solely on natural ventilation to improve the influence of clothing pollution sources on indoor air quality.

Background. Allergic fungal airway diseases, such as asthma and allergic bronchopulmonary mycosis (ABPM), are often difficult to manage with medical treatment alone; therefore, environmental fungal exposure should be accurately evaluated and minimized. In the present study, we established a method to evaluate and eliminate fungal contamination in household air conditioners (ACs). Methods. In the fall of 2020, an environmental survey of living rooms was conducted in 17 Japanese residences of patients with ABPM or related diseases. Household ductless minisplit AC units were disassembled to collect swab samples from the internal parts (filter, heat exchanger, blower fan, and air vent), followed by high-pressure washing. Fungal abundance and composition in swab samples and cleaning effluents of ACs as well as house dust and air samples were determined using quantitative PCR and next-generation sequencing of the internal transcribed spacer 1 region, respectively. A weighted UniFrac distance was calculated to analyze the similarity of the mycobiome among the samples. Results. All interior parts of ACs contained high levels of fungal DNA, with the blower fans being the most contaminated parts. Cladosporium and Toxicocladosporium, followed by Aureobasidium, Aspergillus, and Rhodotorula, were the most common fungi detected in the AC unit. High-pressure washing decreased fungal abundance by over 99% in all AC parts. Fungal abundance and composition in blower fans were strongly correlated with those in cleaning effluents. Conclusion. Interior parts downstream of heat exchangers in household ACs are the major sites of fungal contamination, possibly polluting the indoor air in the residences. High-pressure washing is highly effective for decontamination.

The COVID-19 pandemic outbreak has increased the general awareness of the importance of proper ventilation in the indoor environment to reduce the contagion risk. In particular, attention has been paid to specific categories of buildings, such as schools, due to two factors: (1) high occupancy density and (2) the presence of young and sometimes more susceptible people. Despite the high level of alertness towards the ventilation of classrooms, robust analyses of the effectiveness of the different strategies to mitigate the contagion risk have been difficult to perform. Indeed, the COVID-19 pandemic is still ongoing, and many factors, such as the presence of multiple viral strains, use of facial masks, progression in vaccination, and installation of air purifiers and other sanitization devices, make it difficult to fully quantify the impact of room ventilation by simply analysing available monitoring data. Moreover, mitigation strategies related to ventilation are often dynamic, increasing the complexity of the problem to assess. In this framework, this work proposes a new Monte Carlo method integrated with building performance simulation to evaluate the number of infected occupants under different scenarios, considering also the dynamic boundary conditions. The described approach has been applied to a case study classroom at the Free University of Bozen-Bolzano, Italy, analysing almost 100 different scenarios and discussing the effectiveness of different ventilation strategies traditionally adopted to ensure suitable IAQ according to CO₂ concentration limits. Results highlight the importance of combining different solutions (e.g., mixed-mode ventilation and facial masks) to limit the risk for both students and lecturers.

A large amount of surgical smoke in electrosurgery seriously deteriorates the clean environment of the operating room and can potentially harm medical staff and patients. Exploring the distribution and removal of indoor particulate matter and selecting efficient ventilation patterns are effective ways to control harmful smoke. Therefore, in this study, we combined simulations and full-scale experiments to quantitatively explore the high-concentration spatial regions of particles and compared three ventilation patterns: vertical laminar airflow (VLAF), horizontal laminar airflow (HLAF), and hybrid ventilation, wherein unidirectional airflow (UDAF) was applied to the operating table along with peripheral mixing (UDAF + mixing). We found that simple laminar flow ventilation was significantly affected by the equipment layout and air change rate (air changes per hour; ACH), and the smoke particles were distributed in large amounts in the operating area and could not be removed completely. Conversely, hybrid ventilation can work effectively, and the optimal ACH is approximately 60, which can remove nearly 72% of smoke particles. The airflow distribution in the operating room is also an important factor affecting the distribution and removal of smoke particles. Therefore, medical staff should avoid prolonged exposure to areas with high particle concentrations and particle removal paths.